The Huttonian “Earth Machine”

Basic Idea: Cyclic Changes repeated over and over

• Denudation of Mountains
  • Water, wind loosen and transport material
• Sediment Deposition
  • Ultimately in the ocean
  • Buried by overlong sediments
• Alteration into Sedimentary Rocks
  • Identified two basic means of consolidation
    • Congelation: due to heat
    • Accretion: due to water
  • Argued for alternation by heat
    • Silicate minerals do not dissolve easily
    • Heat can escape more easily than water
    • Heating rocks makes them soft, and easier to compress
• More alteration into Igneous Rocks
  • Additional heating will melt sediments
  • Form crystalline rocks by cooling of melt
  • On-going process
  • Suggests crystalline rocks can be young, as proven by veins that cross-cut other rocks.
• Uplift to form Mountains
  • Call on heat to cause rocks to expand
  • Basically grow by absorbing heat
  • Echo of Aristotle here!

Potential Problems

• Heat Model
  • Two opposing forces
    • Gravity: consolidates
    • Heat: expanses
  • Heat ultimately derived from the sun
  • Outdate by later 18th century
• General assumption of a stable earth
  • No models for active uplift except for volcanic eruptions
  • Not clear why uplift is needed
• Not linked to developing a history based on rocks
  • Process without explaining the basic “Archaic Rock Scale”
• Deism
  • Human habitation must be maintained over indefinite but long time scale
  • Moves beyond the “unidirectional” theories that were commonly accepted (even if relatively long)
• Evidence for pervasive effect of heat, particularly as an agent of uplift (beyond the odd volcano)
• Logic of presentation
  • His use of “eliminative induction” was not accepted in an age of induction-based models derived from field evidence.
• Presentation style
  • Follows the tradition of the “Theories of the Earth” (Cosmologies) that was discredited as having much value.
  • Did not include his own (remarkable) field work
  • Confusing and long-winded
  • This was essentially “natural philosophy” with outdated science and lacking his “natural history” evidence

Notable contributions

• Conceptual advances
  • Unconformities
  • Igneous intrusions
  • Idea of a rock cycle
  • Long time scale and what it might mean
• Must note his remarkable field studies to test his model
• As geology developed circa 1805-30, many of his ideas would be incorporated